JavaWeb-Filter

时间：2020-04-25 16:44:40 阅读：76 评论：0 收藏：0 [点我收藏+]

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过滤器Filter

参考视频: https://www.bilibili.com/video/BV12J411M7Sj?p=24

Filter：过滤器，用来过滤网站的数据。

处理中文乱码
登陆验证

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路径

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依赖

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <parent>
        <artifactId>JavaWeb</artifactId>
        <groupId>com.huangdekai</groupId>
        <version>1.0-SNAPSHOT</version>
    </parent>
    <modelVersion>4.0.0</modelVersion>

    <artifactId>0008_filter</artifactId>

    <dependencies>
        <!--   Servlet的依赖     -->
        <dependency>
            <groupId>javax.servlet</groupId>
            <artifactId>servlet-api</artifactId>
            <version>2.5</version>
        </dependency>

        <!--   JSP依赖     -->
        <dependency>
            <groupId>javax.servlet.jsp</groupId>
            <artifactId>javax.servlet.jsp-api</artifactId>
            <version>2.3.3</version>
        </dependency>

        <!--    JSTL表达式的依赖           -->
        <dependency>
            <groupId>javax.servlet.jsp.jstl</groupId>
            <artifactId>jstl-api</artifactId>
            <version>1.2</version>
        </dependency>

        <!--   standard标签库     -->
        <dependency>
            <groupId>taglibs</groupId>
            <artifactId>standard</artifactId>
            <version>1.1.2</version>
        </dependency>

        <!--   连接数据库     -->
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>5.1.47</version>
        </dependency>
    </dependencies>

</project>

代码

CharacterEncodingFilter

package com.huangdekai.JavaWeb.filter;

import javax.servlet.*;
import java.io.IOException;

/**
 * @Autord: HuangDekai
 * @Date: 2020/4/25 1:34
 * @Version: 1.0
 * @since: jdk11
 */
public class CharacterEncodingFilter implements Filter {

    // 初始化 Web服务器启动，就已经初始化了，等待过滤对象出现
    public void init(FilterConfig filterConfig) throws ServletException {
        System.out.println("CharaterEncodingFilter已经初始化了");
    }

    // chain：链
    /*
    * 1.过滤器中的所有代码，在过滤特定请求的时候都会执行
    * 2.必须要让过滤器继续进行
    * */
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
        servletRequest.setCharacterEncoding("utf-8");
        servletResponse.setCharacterEncoding("utf-8");
        servletResponse.setContentType("text/html;charset=UTF-8");

        System.out.println("CharacterEncodingFilter执行前...");
        filterChain.doFilter(servletRequest, servletResponse);//让请求继续走，如果不写，请求在这里就被拦截停止了
        System.out.println("CharacterEncdoingFilter执行后...");
    }

    // 销毁 web服务器关闭，filter销毁
    public void destroy() {
        System.out.println("CharaterEncodingFilter已经销毁了");
    }
}

CharacterEncdoingFilter是过滤器，很显然，功能就是处理中文乱码的问题。注意继承的是javax.servlet.Filter：

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ShowServlet：

package com.huangdekai.JavaWeb.servlet;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

/**
 * @Autord: HuangDekai
 * @Date: 2020/4/25 1:48
 * @Version: 1.0
 * @since: jdk11
 */
public class ShowServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        resp.getWriter().write("你好啊，世界");
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        doGet(req, resp);
    }
}

web.xml

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd"
         version="4.0">
    
    <servlet>
        <servlet-name>ShowServlet</servlet-name>
        <servlet-class>com.huangdekai.JavaWeb.servlet.ShowServlet</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>ShowServlet</servlet-name>
        <url-pattern>/servlet/show</url-pattern>
        <url-pattern>/show</url-pattern>
    </servlet-mapping>

    <filter>
        <filter-name>CharacterEncodingFilter</filter-name>
        <filter-class>com.huangdekai.JavaWeb.filter.CharacterEncodingFilter</filter-class>
    </filter>
    <filter-mapping>
        <filter-name>CharacterEncodingFilter</filter-name>
        <!-- /servlet/* 的意思是只要是/servlet的任何请求，都会经过这个过滤器     -->
        <url-pattern>/servlet/*</url-pattern>
    </filter-mapping>
</web-app>

配置好之后，启动Tomcat，可以在IDEA中发现这段：

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